1. Field of the Invention
This invention relates to the field of electrical signalling apparatus for motor vehicles, and more particularly relates to a signalling apparatus providing turn, braking and caution indicators for agricultural equipment and the like.
2. Description of the Related Art
Motor vehicles such as automobiles or trucks designed to travel over public roads are provided with lights for signalling turns and braking as standard equipment. Typically, such a motor vehicle is provided with a pair of tail or running lights, one near each of the left and right rear sides of the vehicle. These tail lights each include a pair of filaments to permit the running lights to burn at two different intensities. During normal operation, low intensity filaments in the tail lights are energized to indicate the size and position of the vehicle. When the brake pedal is pressed, a brake signal activates high intensity filaments in the tail lights so that the tail lights burn more brightly than when no brake signal is active.
Many vehicles designed to travel over public roads also mount a separate pair of rear turn signal lights (along with a corresponding pair of front turn signal lights), which are positioned near the left and right running lights, respectively. During normal operation, these turn signal lights are dark. The driver signals an intention to make a turn by flashing the turn signal light on the side toward which the driver intends to turn while leaving the other turn signal light dark.
Alternatively, the tail lights of many pickup trucks and other vehicles have dual filaments. Such vehicles signal turns by flashing a high intensity filament in the tail light on the side toward which the driver intends to turn.
American Society of Agricultural Engineers ["ASAE"] standards recommend that slow-moving agricultural equipment have at least two headlamps, at least one red tail lamp and at least two amber flashing warning lamps. Furthermore, it is recommended that such equipment mount passive "slow moving vehicle" emblems as well as reflectors positioned to indicate the width of the equipment.
According to one signalling scheme, one or more red tail lights are used for the position and braking indications, while a pair of amber caution lights are used for the caution and turn indications. When the agricultural equipment is traveling below a predetermined speed (for example, twenty-five miles-per-hour), both caution lights are flashed intermittently. When it is desired to turn, the caution light on the side toward which the equipment is turning continues to flash intermittently, while the caution light on the side opposite the turn goes dark. According to one alternative, braking or a turn is indicated by means of the red tail lights alone, with the caution lights going dark when either braking or a turn is signalled.
According to another alternative, a turn is indicated by flashing the caution light on the side toward which the equipment is turning intermittently while burning the caution light on the side opposite the turn continuously. One disadvantage to this alternative signalling scheme is the risk that a motorist unfamiliar with the ASAE standards will attribute some unwarranted significance to the continuously-burning caution light opposite the direction of turn.
Many automobiles and trucks provide a "hazard" indication, in which the headlights, tail lights and turn signal lights (where present) are all flashed simultaneously. This hazard indication is not a suitable substitute for the combination of tail lights and caution lights discussed above, since it is impractical for a driver of an automobile or truck to indicate a turn while the hazard indication is operating. It should also be noted that it is illegal in some jurisdictions for a truck to operate on a highway with its hazard signals flashing.
Even where a towing vehicle is provided with tail lights, rear turn lights and caution lights, these may be obscured if the towing vehicle is used to tow another large vehicle. Thus, it is common practice for newer motor vehicles to include plugs for connecting lights mounted on the towed vehicle to one or more of the tail, brake, turn and caution signals of the towing vehicle. Different vehicles have different plug configurations for making such connections.
One plug configuration, common in pickup trucks, includes four contacts, one for ground, one for the tail signal, and two which carry both the brake signal and the turn signals. The latter two contacts are inactive when the brake and turn signals are both off. When the brake pedal is pressed and no turn is being signalled, both of the latter two contacts supply a steady signal. When a right or left turn is being signalled without the brake pedal being pressed, one of the latter two contacts supplies an intermittent flashing signal while the other is inactive. When a turn is intended and the brake pedal is being pressed, one of the latter two contacts supplies a flashing signal while the other supplies a steady signal. None of the contacts in this configuration supplies a caution indication.
Another plug configuration, common in farm tractors and other agricultural equipment, includes four contacts, one for ground, one for the tail signal and two which carry both the turn signals and a caution indication signal. If the vehicle is running but no turn is being indicated, the latter two contacts each supply an intermittent flashing signal to provide a caution indication. When a right or left turn is to be signalled, a corresponding one of the latter two contacts supplies the flashing signal while the other supplies no signal. This configuration does not supply a brake signal.
For convenience, this specification will refer to the signals conducted by either the truck or tractor plug configurations as "ground," "tail" and "turn" signals. Note that the turn signals described in connection with the truck or tractor plugs may combine turn and braking indications, as in the truck plug configuration, or turn and caution indications, as in the tractor plug configuration.
While tail lights, turn lights and caution lights are currently standard equipment on farm tractors, this has not always been the case. Many tractors still in service were manufactured before tail lights, turn lights and caution lights became standard equipment. On occasion, one still sees a farm tractor operated on a public road with only reflectors to indicate its size, position and speed.
There remains a need for a signalling apparatus which is quickly and easily coupleable to either a truck or tractor plug configuration to provide standard tail, brake, turn and caution indications for self-propelled or towed agricultural equipment. In addition, there remains a need for a signalling apparatus capable of providing intermittent caution indicators when the equipment is moving below a minimum speed and de-activating the intermittent caution indicators when the vehicle is operated at higher speed.
U.S. Pat. No. 4,006,453 to Bryant proposes a device for adapting combined brake and turn signal lights on a trailer to independent brake signal and turn signal lights on a towing vehicle. The device has two circuits, one for each side, each circuit having a brake signal switch. The brake signal switches are selectively actuated by impulses received from the corresponding turn signal flashers on the vehicle, to block the brake signal current to the corresponding signal light on the trailer. Bryant does not address the problem of generating a flashing signal to two or more caution indicators on the rear of an agricultural vehicle when neither braking nor a turn is being indicated; instead, Bryant appears to address the separate problem of independently interrupting a constant braking signal, on one side of the vehicle only, when the driver signals a turn.